Search

Azerbaijan is one of the oldest oil and gas provinces, where more than 2 bln tons of oil have been extracted over more than a century. At present, the oil production is declining and mainly determined by production from the Azeri-Chirag-Guneshli offshore block (AChG). Compared to oil, the opportunities for further growing natural gas reserves and production are very promising. For the latest years, a number of large gas condensate fields have been discovered in the deep-water part of South Caspian Sea, such as Shakh-Deniz, Apsheron, Umid. There are a number of prospects that have not yet been drilled in this part of the sea basin. The paper assesses their prospectivity, substantiates the priority exploration targets and, on the basis of the statistical analysis of the quantitative gas/oil ratio data for many other Azerbaijanian and world basins, an attempt is made to assess the reserves in the prospects. The total recoverable oil reserves in Azerbaijan are estimated at 3.5 bln tons, of which slightly above 2 bln tons have already been extracted. Based on the statistically estimated ratio between the volumes of gas and oil in various basins of the world, including Azerbaijan, the total possible natural gas reserves in Azerbaijan are estimated at about 4 trillion m3 . This is in agreement with the other available estimates. Of this volume of natural gas, 0.85 trillion m3 has already been extracted, and the approved geological reserves are estimated at 2.55 trillion m3 . Almost 83% of the extracted natural gas belonged to offshore fields. This trend will continue in the future, and, moreover, will be strengthened due to large volumes of gas condensate accumulations in the deepwater part of the basin. In this part of the basin, the most attractive prospects are Mashal, Shafag, and Israfil Huseynov, total reserves of which are expected at 0.6 trillion m3 of natural gas.

The Albertine Graben, an active sedimentary petroliferous basin, has gained global attention as the unexplored areas are recently being targeted for hydrocarbon prospectivity. Here, we present the first detailed geological investigation of the Upper Miocene–Pliocene clastic interval in the southern Lake Albert, part of the Semliki Basin. We employed an integrated approach that includes source rock evaluation, reservoir characterization, pore pressure, and geomechanical evaluation. Thermal maturity analyzed from vitrinite reflectance, spore color index, and Rock–Eval Tmax indicates that the Lower Kasande–Kakara shales are into the early catagenetic maturity, and the onset of oil window occurs at around 2550 m. With 1.8–2.4% total organic carbon content and dead carbon-free hydrogen index of ~ 600 mg S2/g TOC, a Type I/II oil-prone source rock was inferred, while the state of the thermal maturity reflects on the relatively low free oil yields associated with a poor oil production index. The quartz arenite reservoirs of the Upper Miocene Kasande–Kakara Formation exhibit excellent petrophysical characteristics and possess pore pressure gradients of 0.17–0.24 psi/ft (1 psi/ft = 22.6206 Mpa/km) in two distinct zones (2040.7–2221.5 m and 2554.7–2730 m) with gross vertical thickness of ~ 206 m. The region belongs to a normal faulting tectonic regime where the vertical stress gradient is 0.91–0.93 psi/ft with a lower bound of minimum horizontal stress gradient interpreted as 0.62 psi/ft. The hydrostatically pressured Miocene shales have higher shear failure gradients and exhibited extensive wellbore failures. The implications of geological characterization in both hydrocarbon exploration and future drilling in the basin are envisaged in this research.

Machine learning (ML) as a powerful data-driven method is widely used for mineral prospectivity mapping. This study employs a hybrid of the genetic algorithm (GA) and support vector machine (SVM) model to map prospective areas for Au deposits in Karamay, northwest China. In the proposed method, GA is used as an adaptive optimization search method to optimize the SVM parameters that result in the best fitness. After obtaining evidence layers from geological and geochemical data, GA–SVM models trained using different training datasets were applied to discriminate between prospective and non-prospective areas for Au deposits, and to produce prospectivity maps for mineral exploration. The F1 score and spatial efficiency of classification were calculated to objectively evaluate the performance of each prospectivity model. The best model predicted 95.83% of the known Au deposits within prospective areas, occupying 35.68% of the study area. The results demonstrate the effectiveness of the GA–SVM model as a tool for mapping mineral prospectivity.

Over the last two decades, Mineral Resources Tasmania has been developing regional 3D geological and geophysical models for prospective terranes at a range of scales and extents as part of its suite of precompetitive geoscience products. These have evolved in conjunction with developments in 3D modeling technology over that time. Commencing with a jurisdiction-wide 3D model in 2002, subsequent modeling projects have explored a range of approaches to the development of 3D models as a vehicle for the better synthesis and understanding of controls on ore-forming processes and prospectivity. These models are built on high-quality potential field data sets. Assignment of bulk properties derived from previous well-constrained geophysical modeling and an extensive rock property database has enabled the identification of anomalous features that have been targeted for follow-up mineral exploration. An aspect of this effort has been the generation of uncertainty estimates for model features. Our experience is that this process can be hindered by models that are too large or too detailed to be interrogated easily, especially when modeling techniques do not readily permit significant geometric changes. The most effective 3D modeling workflow for insights into mineral exploration is that which facilitates the rapid hypothesis testing of a wide range of scenarios whilst satisfying the constraints of observed data.

Thanks to the brilliant progress in machine learning, many research works have conducted data-driven mineral prospectivity mapping. However, it is challenging to integrate highly multidisciplinary geoscientific data with machine learning algorithms. Especially, geological data are heterogeneous and non-numerical even though they are crucial for mineral exploration. In this work, we introduce how to preprocess the geoscientific data and design a machine learning model based on knowledge to make the best use of both geoscientific information and the advantages of machine learning. We focus on the region-scale prospectivity mapping for the komatiite-hosted nickel in Yilgarn craton, Western Australia. We extract second and thirdorder features from geophysical data to enable machine learning models to capture various patterns of mineral deposits. In terms of geology, faults, interpreted geology, and isotopic mapping data are converted into numerical features that could be related to the komatiite-hosted nickel deposits. Based on domain knowledge, we design a deep learning model that systemically combines geophysical and geological features. First, our model generates a feature map and initial prospectivity map using geological data and geophysical worms which could reveal the crustal structures. Next, the model produces a final prospectivity map that delineates potential komatiite-hosted nickel deposits using whole data including geophysics. The model is trained with the locations of the known nickel deposits. We divide the Yilgarn craton area into a train and test region to validate our model. We adopt the AUC score and prospectivity score percentile of known deposits to evaluate our model in various aspects. Our model achieved a high AUC and percentile score and it can be efficiently used for early-stage nickel exploration. The suggested workflow could be applied to the exploration of the other mineral types with a slight modification reflecting the characteristics of the mineralizations., Open-Access Online Publication: March 01, 2023

The accuracy of data-driven predictive mineral prospectivity models relies heavily on the training datasets used. These models are usually trained using data for “known” deposit locations as well as “non-deposit” locations that are based on randomly generated point patterns. In this study, data related to the Seabridge Gold Inc Iskut project, an epithermal Au deposit in northwestern British Columbia (BC), Canada, are used to test the utility of data-driven mineral prospectivity modeling. The input spatial dataset is comprised mostly of publicly available data. Data for 18 vein and epithermal Au known mineral occurrences (KMO) are obtained from the BC Geological Survey’s MINFILE repository and selected as training deposit locations. A total of eleven sets of non-deposit locations (NDL) were also created, including one set of selected non-prospective KMO for Au deposits from the MINFILE and ten sets of random point patterns. Given the scale of this study, most of the KMO recorded on the property are of the epithermal deposit type. Hence, they could not be used as a selection criterion. Data-driven mineral potential models are generated using the random forest (RF) algorithm and trained on multiple data sets. The comparison of RF models demonstrated that using non-prospective KMO generates more accurate predictions than the random point pattern. The produced mineral prospectivity maps delineated multiple areas with higher discovery potential, which matched viable targets for the Au-Cu epithermal-porphyry system identified through previous Seabridge Gold Inc. (Toronto, ON, Canada) field reconnaissance and drilling programs.

The article deals with the prospects of Iraq’s oil and gas potential. It should be noted that there has not been much attention payed to the desert regions of Iraq located on the Arabian plate. However, recent studies show prospectivity of the Iraq deserts. As a result of the recent investigation of river valleys in the region, the following main morphotectonic processes were identified: rejuvenation of the river network and emergence of new river basins; division of individual rivers into two or more parts; interception of the river network. As a result of long-term field and cameral geological and geomorphological studies in the area of the Western and Southern deserts, it was possible to reconstruct the existing tectonic activity of the area from the Miocene period to the present day. It is established that the regional Euphrates fault on the territory of Iraq occupies an exceptionally important place, which was previously underestimated. Adjacent echelon faults of the following order formed a system of pre-existent tectonic blocks with different kinematics and morphology. The causes and mechanism of neotectonic Neogene-Quaternary movements of the earth’s surface are established. Thus, separate tectonic blocks are identified, which generally form zonal regions of uplifts or valleys. The areas of elevated blocks (for example, the raising of Al-Najaf Al-Ashraf of the third order) are created by plicative dome structures in the cover near the Euphrates fault, favorable for the accumulation of HC.

Field development is a very costly endeavor that requires drilling several wells in an attempt to understanding potential prospects. To help reduce the associated cost, this study integrates well and seismic based rock physics analysis with artificial neural network to evaluation identified prospects in the field. Results of structural and amplitude maps of three major reservoir levels revealed structural highs typical of roll over anticlines with amplitude expression that conforms to structure at the exploited zone where production is currently ongoing. Across the bounding fault to the prospective zones, only the D_2 reservoir possessed the desired amplitude expression, typical of hydrocarbon presence. To validate the observed amplitude expression at the prospective zone, well and seismic based rock physics analyses were performed. Results from the analysis presented Poisson ratio, Lambda-Rho and Lambda/Mu-Rho ratio as good fluid indicator while Mu-Rho was the preferred lithology indicator. These rock physics attributes were employed to validate the observed prospective direct hydrocarbon indicator expressions on seismic. Reservoir properties maps generated for porosity and water saturation prediction using Probability Neural Network gave values of 20-30% and 25-35% for water saturation and porosity respectively, indicating the presence of good quality hydrocarbon bearing reservoir at the prospective zone.

This study focusses on the sedimentological and aeromagnetic characteristics within the Agbaja Ironstone Formation to establish the sedimentary depositional history and map oolitic ironstone zones in the Lokoja district of the Nupe Basin. Forty sandstone samples were collected for granulometric, sedimentary facies and petrographic analyses to reconstruct depositional processes of the Agbaja Ironstone Formation. Aeromagnetic data analysis was engaged to map the oolitic ironstone rich zones. The iron-rich sandstones in the Agbaja Ironstone Formation occur as oolitic ironstone, ironstone concretion and laterites. The bivariate grain size plots and multivariate discriminant analyses suggest that 92% of the sandstone in the formation were deposited in beach and coastal dunes under fluvial-river actions, while 8% are of the marine environment deposited under wave actions. The quartz-feldspar lithic (QFL) ternary diagram and palaeocurrent analyses of the samples revealed that the matured, sub-arkosic sandstones originated from the cratonic interior (Abakaliki uplifts). The bioturbation and reactivation by Ophiomorpha burrows and herringbone on the fine-medium grained sandstones in the formation contributed to the observed high magnetic intensity values. High magnetic signatures (−94.784 to 1.191 nT), analytic signal peaks and depth levels from the 2-D source parameter images are the basis for the produced oolitic ironstones prospectivity map in this study.

Selecting internal hyperparameters, which can be set by the automatic search algorithm, is important to improve the generalization performance of machine learning models. In this study, the geological, remote sensing and geochemical data of the Lalingzaohuo area in Qinghai province were researched. A multi-source metallogenic information spatial data set was constructed by calculating the Youden index for selecting potential evidence layers. The model for mapping mineral prospectivity of the study area was established by combining two swarm intelligence optimization algorithms, namely the bat algorithm (BA) and the firefly algorithm (FA), with different machine learning models. The receiver operating characteristic (ROC) and prediction-area (P-A) curves were used for performance evaluation and showed that the two algorithms had an obvious optimization effect. The BA and FA differentiated in improving multilayer perceptron (MLP), AdaBoost and one-class support vector machine (OCSVM) models, thus, there was no optimization algorithm that was consistently superior to the other. However, the accuracy of the machine learning models was significantly enhanced after optimizing the hyperparameters. The area under curve (AUC) values of the ROC curve of the optimized machine learning models were all higher than 0.8, indicating that the hyperparameter optimization calculation was effective. In terms of individual model improvement, the accuracy of the FA-AdaBoost model was improved the most significantly, with the AUC value increasing from 0.8173 to 0.9597 and the prediction/area (P/A) value increasing from 3.156 to 10.765, where the mineral targets predicted by the model occupied 8.63% of the study area and contained 92.86% of the known mineral deposits. The targets predicted by the improved machine learning models are consistent with the metallogenic geological characteristics, indicating that the swarm intelligence optimization algorithm combined with the machine learning model is an efficient method for mineral prospectivity mapping.

The aim of the work was to conduct an agro-ecological assessment of agricultural lands, select a typical test area by key indicators, and conduct a comprehensive analysis with the mapping of the utilisation efficiency of this area. The aim of this work was to demonstrate the fundamental possibility of solving socio-economic and environmental problems of the land use in the context of reforming the land and property complex by the example of a specific project. The algorithm of the land management actions for efficient economic use of the territory of the key site has been offered. The proposed measures are based on the organisation of an arable land with the allocation of field, grain-grass and soil-protective crop rotations, grassing-down of spillways, and conservation of a low-productive arable land, design of a field-protective forest range, determination of the type of use of natural forage lands, allocation of places for the implementation of erosion-hazardous agricultural land afforestation, organisation of a bee park, clumps of broadleaves and micro-reserves. The prospectivity of transition from a spatial object of lands assessment to their agro-ecological type by means of morphometric analysis of the terrain using GIS-technologies, calculation of territory roughness, determination of the erosion potential of the terrain, and complex integration of the results into the typification of agro-climatic resources has been proved. The prospectivity of use of soil-recovering effects for the development of new models of resource-saving sustainable agriculture has been demonstrated.

In many basins, hydrogen-emitting structures are now observed, but the estimation of the H2 flow leading to their formation remains poorly constrained since all data show that the H2 emissions are variable in space and time. We present here the data of a long-term monitoring campaign with a high density of permanent hydrogen detectors installed in 2 structures in the Minas Gerais State (Brazil). Results show that two kinds of signals are recorded, large sporadic pulses that affect the H2 content of the soil for one or two days and smaller ones, with a daily periodicity, that last 6 h and during which the near surface soil concentration usually does not exceed 200 ppm. This last signal is very regular in frequency, less in amount, and the daily maximum happens around noon or in the early afternoon. We interpret the large pulses as evidences of a deep hydrogen flux, leaking either from a reservoir located in the subsurface, from an aquifer which is degassing or, although it seems unlikely, directly from the H2 generation area. The time correlation between the pulse and the increase of the daily signal suggests that this last one corresponds to the slow release of the gas that has been captured by the soil during its transport towards the surface. This daily signal is most likely influenced by external factors such as atmospheric pressure and sub-surface bacterial activity. In map view, the lack of correlation between the highest hydrogen concentrations over time suggests that the soil is very heterogeneous and that preferential pathways exist. The results confirm that long-term monitoring, over a few months, is mandatory to catch a certain number of high pulses and so to have a better estimation of the real flow. Data also suggests that sensors with a large concentration range should be used (from 10 to several 104 ppm). Even if quantification of leakage doesn't help to quantify the subsurface reserves, these new data allow a more precise evaluation of the quantity of H2 released in surface by these structures, few hundred of kilo per day, and confirm the high H2 prospectivity of this basin.

International audience; This study details new geochemical analysis from an outcrop in Crete to improve understanding of the hydrocarbon potential of the southern margin of the Hellenic Arc along the continental convergent zone of the central Mediterranean Ridge. Seventeen samples were collected from the Late Miocene sub-salt sedimentary succession of Plouti section in central Crete and were studied in terms of their organic geochemical features using Rock-Eval VI pyrolysis. Results of this investigation revealed intervals with sufficient organic material of good enough quality and quantity to be considered as potential source rocks. The obtained data generally present poor to fair and/or good in some cases hydrocarbon generation potential. The TOC values range from 0.03 to 1.99%, with an average fair (2.1 mg HC/g rock) hydrocarbon potential. A Type III kerogen was identified, indicating a terrestrial origin organic matter. T max and Production Index values suggest that the most promising parts of the section (organic-rich sediments) are immature with respect to oil generation and have not experienced high temperature during burial. Overall, the present study offers the opportunity to advance our understanding on the hydrocarbon potential onshore Crete and further investigate hydrocarbon prospectivity in the adjoining area, and particularly, the Greek part of the Mediterranean Ridge, a region with crucial economic and strategic importance.

The Labrador Trough in northern Quebec is currently the focus of ongoing exploration for magmatic Ni-Cu-platinum group element (PGE) sulphide ores. This geological belt hosts voluminous basaltic sills and lavas of the Montagnais Sill Complex, which are locally emplaced among sulphidic metasedimentary country rocks. The recently discovered Idefix PGE-Cu prospect represents a stack of gabbroic sills that host stratiform patchy disseminated to net-textured sulphides (0.2–0.4 g/t PGE+Au) over a thickness of ∼20 m, for up to 7 km. In addition, globular sulphides occur at the base of the sill, adjacent to the metasedimentary floor rocks. Whole-rock and PGE geochemistry indicates that the sills share a common source and that the extracted magma underwent significant fractionation before emplacement in the upper crust. To develop the PGE-enriched ores, sulphide melt saturation was attained before final emplacement, peaking at R factors of ∼10 000. Globular sulphides entrained along the base of the sill ingested crustally derived arsenic and were ultimately preserved in the advancing chilled margin.

Small intrusions dominated by olivine- and pyroxene-rich cumulates are well known to be favorable hosts to magmatic Ni-Cu-(Platinum Group Element—PGE) sulfide mineralization. Such intrusions are common in a variety of settings around the world, but only a very small proportion contain economically exploitable sulfides; these tend to be of conduit or chonolith style. If prospectivity could be discriminated from sparse sampling at early exploration stages, then the discovery rate for deposits of this type could be improved. To this end, a number of pyroxene-bearing samples from small intrusions containing magmatic sulfide deposits have been investigated including the Noril'sk-Talnakh camp in Siberia, the Kotalahti nickel belt in Finland, Ntaka Hill in Tanzania, Nova-Bollinger in the Albany-Fraser Orogen of Australia, Savannah in the Halls Creek Orogen of Australia, Jinchuan in central China, Xiarihamu in Tibet and Huangshanxi in the east Tianshan Ni province of NW China. To compare, samples from unmineralized intrusions in four of these regions were also investigated along with four mafic intrusions from other localities that are not associated with any known economic sulfide mineralization. Using fine-scale (

Nuclear power has the potential to provide significant amounts of reliable electricity generation without carbon dioxide emissions. Disposing of radioactive waste is, however, an ongoing challenge, and if it is to be buried, the characterisation of the regional groundwater system is vital to protect the anthroposphere. This aspect is understudied in comparison to the engineered facility; yet, selecting a suitable groundwater setting can ensure radionuclide isolation hundreds of thousands of years beyond that provided by the engineered structure. This paper presents a multi-faceted scoping tool to quantitatively assess, and directly compare, the regional hydrogeological prospectivity of different groundwater settings for disposal at an early stage of the site selection process. The scoping tool is demonstrated using geological data from three distinct UK groundwater settings as a case study. Results indicate a significant difference in the performance potential of different regional groundwater settings to ensure long-term waste containment.

Antimony (Sb) is a critical metal for Europe. Indeed, Sb is widely used in a variety of industrial operations, especially in the European aircraft industry, such as production of flame retardants, plastics, paint pigments, glassware and ceramics, alloys in ammunition and battery manufacturing plants.Despite its strategic importance, the knowledge on Sb and its ore deposits remains poorly constrained. Moreover, Europe remains under the threat of an essentially Chinese supply despite a proven potential for European deposits that contain also strategic and precious co-products (W, Au). In parallel, Sb and associated metalloids (As, Hg, etc) are more and more recognised as a global threat for human health and it has been demonstrated that most of elevated concentrations of Sb on earth surface originate from natural, geogenic sources. Then, a first large-scale identification of these areas where primaries resources occur and metalloids can contaminate humans should be a priority.To achieve its objectives, the overall approach of the ERA-MIN2 AUREOLE project (2019-2022 - https://aureole.brgm.fr) is based on disruptive concepts: i) development of a 3D large-scale metallogenic model integrating deep-seated processes to determine the spatial distribution of ore deposits; ii) the use of mineral prospectivity data weighted by surface data to determine the probability of environmental risk over large areas.The work package (WP) 1 is dedicated to produce the new 3D deep-seated metallogenic model for antimony mineralisations and contribute to the global 3D understanding of the Sb mineralising processes. The WP2 is designed to the understanding of processes - such as geomorphology, weathering, climate - that control the mobilisation and transport of metalloids at the earth surface. The WP3 will use results from WPs 1 & 2 to produce large-scale mineral prospectivity and a large-scale environmental risk assessment by weighting mineral prospectivity with earth surface properties, such as DTM, rainfall, weathering cartographic maps, etc.The AUREOLE project will bring new scientific knowledge on Sb and Sb deposits, for a better mineral exploration targeting.The expected outcomes will be several high-impact deliverables devoted to the targeting of new Sb deposits and a new large-scale environmental assessment maps for decision-making dealing with humans health. Long term expected impacts would be an increase of EU Sb resources and EU Sb sustainable supply. Because of its implications for European critical metals, the AUREOLE project will provide new findings and results to the SCRREEN project (Solutions for Critical Raw Materials – a European Expert Network) and to the IMP@CT project (Integrated Mobile Modularised Plant and Containerised Tools for sustainable, selective, low-impact mining of small, high-grade or complex deposits). It will also interact with the Geo-ERA FRAME project (Forecasting and assessing Europe’s strategic raw materials needs).

There are a significant number of image processing methods that have been developed during the past decades for detecting anomalous areas, such as hydrothermal alteration zones, using satellite images. Among these methods, dimensionality reduction or transformation techniques are known to be a robust type of methods, which are helpful, as they reduce the extent of a study area at the initial stage of mineral exploration. Principal component analysis (PCA), independent component analysis (ICA), and minimum noise fraction (MNF) are the dimensionality reduction techniques known as multivariate statistical methods that convert a set of observed and correlated input variables into uncorrelated or independent components. In this study, these techniques were comprehensively compared and integrated, to show how they could be jointly applied in remote sensing data analysis for mapping hydrothermal alteration zones associated with epithermal Cu–Au deposits in the Toroud-Chahshirin range, Central Iran. These techniques were applied on specific subsets of the advanced spaceborne thermal emission and reflection radiometer (ASTER) spectral bands for mapping gossans and hydrothermal alteration zones, such as argillic, propylitic, and phyllic zones. The fuzzy logic model was used for integrating the most rational thematic layers derived from the transformation techniques, which led to an efficient remote sensing evidential layer for mineral prospectivity mapping. The results showed that ICA was a more robust technique for generating hydrothermal alteration thematic layers, compared to the other dimensionality reduction techniques. The capabilities of this technique in separating source signals from noise led to improved enhancement of geological features, such as specific alteration zones. In this investigation, several previously unmapped prospective zones were detected using the integrated hydrothermal alteration map and most of the known hydrothermal mineral occurrences showed a high prospectivity value. Fieldwork and laboratory analysis were conducted to validate the results and to verify new prospective zones in the study area, which indicated a good consistency with the remote sensing output. This study demonstrated that the integration of remote sensing-based alteration thematic layers derived from the transformation techniques is a reliable and low-cost approach for mineral prospectivity mapping in metallogenic provinces, at the reconnaissance stage of mineral exploration.

© 2020 by the authors. The exploration of carbonate-hosted Pb-Zn mineralization is challenging due to the complex structural-geological settings and costly using geophysical and geochemical techniques. Hydrothermal alteration minerals and structural features are typically associated with this type of mineralization. Application of multi-sensor remote sensing satellite imagery as a fast and inexpensive tool for mapping alteration zones and lithological units associated with carbonate-hosted Pb-Zn deposits is worthwhile. Multiple sources of spectral data derived fromdifferent remote sensing sensors can be utilized for detailed mapping a variety of hydrothermal alteration minerals in the visible near infrared (VNIR) and the shortwave infrared (SWIR) regions. In this research, Landsat-8, Sentinel-2, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and WorldView-3 (WV-3) satellite remote sensing sensors were used for prospecting Zn-Pb mineralization in the central part of the Kashmar-Kerman Tectonic Zone (KKTZ), the Central Iranian Terrane (CIT). The KKTZ has high potential for hosting Pb-Zn mineralization due to its specific geodynamic conditions (folded and thrust belt) and the occurrence of large carbonate platforms. For the processing of the satellite remote sensing datasets, band ratios and principal component analysis (PCA) techniques were adopted and implemented. Fuzzy logic modeling was applied to integrate the thematic layers produced by image processing techniques for generating mineral prospectivity maps of the study area. The spatial distribution of iron oxide/hydroxides, hydroxyl-bearing and carbonate minerals and dolomite were mapped using specialized band ratios and analyzing eigenvector loadings of the PC images. Subsequently, mineral prospectivity maps of the study area were generated by fusing the selected PC thematic layers using fuzzy logic modeling. The most favorable/prospective zones for hydrothermal ore mineralizations and carbonate-hosted Pb-Zn mineralization in the study region were particularly mapped and indicated. Confusion matrix, field reconnaissance and laboratory analysis were carried out to verify the occurrence of alteration zones and highly prospective locations of carbonate-hosted Pb-Zn mineralization in the study area. Results indicate that the spectral data derived from multi-sensor remote sensing satellite datasets can be broadly used for generating remote sensing-based prospectivity maps for exploration of carbonate-hosted Pb-Zn mineralization in many metallogenic provinces around the world.

The Axi low-sulfidation (LS) epithermal deposit in northwestern China is the result of geological controls on hydrothermal fluid flow through strike-slip faults. Such controls occur commonly in LS epithermal deposits worldwide, but unfortunately, these have not been quantitatively analyzed to determine their spatial relationships with gold distribution and further guide mineral prospecting. In this study, we conduct a 3D mineral prospectivity modeling approach for the Axi deposit involving 3D geological modeling, 3D spatial analysis, and prospectivity modeling. The spatial analysis of geometric features revealed the gold mineralization trends in convex segments (0&ndash, 20 m) with a specific distance from fault 2, the lower interface of late volcanic phase, and the upper interface of phyllic alteration with steep slopes (&gt, 65&deg, ), implying that gold deposition was significantly controlled by the morphological characteristics and distance fields of geologic features. The present alteration&ndash, mineralization zone at Axi has a larger width in bending sites (sections No. 35&ndash, 15 and No. 40&ndash, 56) than elsewhere, indicating the location of two fluid conduits extending to depth. The prediction-area plots and receiver operating characteristic curves demonstrated that (genetic algorithm optimized support vector regression (GA-SVR)) outperformed multiple nonlinear regression and fuzzy weights-of-evidence, which was proposed as a robust method to solve complicated nonlinear and high-dimensional issues in prospectivity modeling. Our study manifests spatial controls of structure, host rock, and alteration on LS epithermal gold deposition, and highlights the capability of GA-SVR for identifying deposit-scale potential epithermal gold mineralization.

International audience; Geodynamic models, geological-geophysical interpretations, and isotope analysis illustrate that there are links between the nickel and gold mineral systems in the Halls Creek Orogen, Western Australia. Whole-rock Nd and 40Ar/39Ar analysis of rocks throughout the region, when compared with the geodynamic models suggest that nickel and gold mineralization in the Halls Creek Orogen can be related to basin development and subsequent basin closure during the convergence of North Australian Craton and Kimberley Craton, respectively. Whole-rock Nd analysis confirmed the input of juvenile melts in the centre of the orogen before the 1835–1805 Ma Halls Creek Orogeny, supporting the upwelling of decompression mantle melts during the basin development. These analyses also revealed the spatial links between nickel and gold mineralization and lithological units with positive εNd values. Spatially the link between these mineral systems appears to be related to the presence of deep-seated shear zones that formed early in the history of the orogen and were later reactivated. The results of geodynamic models, geophysical interpretation, and isotopic analysis are used to understand the critical processes in the gold and nickel mineralization, which are presented by predictor maps. The GIS-based knowledge-driven fuzzy logic method used to integrate the predictor maps and create the prospectivity maps. Herein we show that mafic-ultramafic units prospective for nickel mineralization formed by upwelling of decompression mantle melt during crustal thinning and extension during basin development, and typically consist of the most juvenile magmas in the region. Whereas, gold deposits formed during the compressional regime and basin closure, and are located along a major shear zone separating two terranes. This deep crustal-scale shear zone is implied to be the site of multiple stages of deformation that acted as fluid migration pathways during basin closure and subsequent collision. Another critical element that appears to be related to gold prospectivity is the presence of lithologies with a juvenile signature. In contrast to nickel analyses which are closely related to mafic-ultramafic units, the source component seems less influential when attempting to target orogenic gold deposits.

[Abstract A glossary of commonly used terms related to the geometric forms and geological settings of basement highs is presented to assist cross‐disciplinary understanding, qualifying prefixes for the term basement are discussed and a scheme for characterising basement highs is presented. This scheme is designed to standardise, and to add rigour to, description of basement highs. It will thereby enhance basement high comparisons and assist understanding of basement highs across technical disciplines. The scheme enables systematic characterisation of: the geometry of a basement high; the lithologic units and structures in, above and around it; timings; tectonics and origins of the basement high and play elements relating to resource prospectivity. Use of this scheme is demonstrated using the southern Rona Ridge (West of Shetland, UK Continental Shelf). The tectonic, isostatic, erosional and stratigraphic processes that form basement highs are also discussed, and examples in proven petroleum systems are presented., Example of geometric features of a basement high, illustrated using the south Rona Ridge 3D Top Basement depth structure map. A = Lancaster Field oil‐water contact at 1678 m true vertical depth sub sea level (TVDSS) (Hurricane Energy, 2019c). B = Lincoln oil discovery “oil down to” at 2258 m TVDSS. C = Whirlwind Discovery “oil down to” at TVDSS. The basement high covers an area of ~ 1200 km , so it is a 4th order basement high. It has an approximately trapezoid shape in map view shape (including the Whirlwind downthrown block). The topography of the upper surface can be described as an undulating wedge (area i) and an undulating planar slope (areas labelled ii). Structures segmenting the basement high include: 1 = Westray Fault Zone; 2 = Brynhild Fault Zone. Contour increment 100 m. ]

In this paper, we present an integrated landform-regolith mapping protocol/chart for West Africa developed using a case from Central Burkina Faso. The chart accounts for (i) the specificities of the ubiquitous, duricrust-capped remnants of the regional paleolandsurfaces – particularly the residual or detrital character of the Fe duricrusts – and (ii) the diversity of the remaining, non-duricrusted portions of the landscape, with an emphasis on the pitfalls encountered in determining the in-situ or transported character of the regolith. The paper also provides field identification criteria and illustrations of the typical West African landform-regolith associations. The landform-regolith mapping chart is integrated into a prospectivity chart, which is used to define exploration guides: (i) defining sampling strategies, (ii) interpreting potential geochemical anomalies and (iii) targeting lateral extensions of known bedrock mineralizations. The mapping protocol further allows for the definition of a class of landform-regolith association propitious to supergene mineral concentrations. The mapping protocol is shown to be transposable to wetter contexts and, more generally, to other tropical shield provinces.

Knowledge of the in situ stress state of the Earth's crust plays a key role in understanding geological processes including plate tectonics, earthquakes, slope failure, and igneous emplacement. In this paper, we determine the in situ stress orientation from the PTA2 borehole on the island of Hawai'i, drilled into a lava flow dominated sequence between Mauna Kea and Mauna Loa. High‐resolution acoustic images were collected from the open hole interval 886 m to 1,567 m. Based on identification of 371 borehole breakouts for a total length of 310 m, the mean orientation of the minimum horizontal principal stress is N106° and remains constant across different volcanic rock fabrics. Changes in borehole breakout shape are linked to the different strength of volcanic facies and intra‐facies. The orientation of the present‐day stress field at Mauna Kea deviates from the plate forces and regional tectonic stress field. We interpret the compressive stress regime at the PTA2 site as resulting from the competing gravitational fields of the large topographic highs of Mauna Kea and Mauna Loa. Our study reveals that the mass accumulation associated with shield volcano growth imparts significant local variations to the subsurface stress state on volcanic islands consisting of overlapping shield volcanoes. The results have significant implications for stress accumulation leading to brittle failure and flank collapse, along with potentially influencing magma accumulation and ascent pathways during volcanic island evolution. This study provides the first insights into the orientation of the present‐day stress field between the major island forming shield volcanoes of Hawai'i.

Studies for the characterization of hydrocarbon reservoirs using well logs have been carried out in the M-Field of the Douala Basin to evaluate the hydrocarbon prospectivity, delineate hydrocarbon zones and determine the petrophysical properties of the identified reservoir rocks. Data from two wells comprising gamma ray, resistivity, neutron, density logs were used. Gamma ray log was used for lithologic discrimination; resistivity log was employed to identify formation fluid based on electrical responses of reservoir formations, while combined density and neutron logs were used to estimate reservoir porosity, as well as ascertain hydrocarbon type where present. Four hydrocarbon bearing reservoirs were delineated in the study area; one in Well-X (X 2) with a thickness of 6.2 m and three others in Well-Y (Y 1, Y 2, Y 3) with thicknesses of 19.2 m, 7.6 m and 78.7 m, respectively. Neutron–density crossplots indicate heterogeneous reservoir matrix comprising of sand, limestone and dolomite. The reservoirs were correlated using gamma ray log and were found to be discontinuous across the wells. The petrophysical parameters of the reservoirs evaluated indicate porosity, water-saturation and hydrocarbon-saturation values of X 2 to be 20.8%, 30.8% and 69.2%, respectively, and the average porosity, water saturation and hydrocarbon saturation of the Well-Y reservoirs to be 40.2%, 18.3% and 81.7%, respectively. The porosity value indicates medium–high formation porosities and oil as the dominant hydrocarbon type. The crossplot of water-saturation and porosity revealed that the grain size variation of the reservoirs ranges from fine-grained to silty sands. The bulk volume water (BVW) values for the M-Field reservoirs suggest that they are homogeneous and at irreducible water saturation (Swirr) and hence will produce water-free hydrocarbons.

Following a regional reconnaissance stream sediment survey that was carried out in the northern Vosges Mountains in 1983, a total of 20 stream sediment samples were collected with the aim of assessing the regional prospectivity for the granite-hosted base and rare metal mineralisation of the northern Vosges magmatic suite near Schirmeck. A particular focus of the investigation was the suspected presence of W, Nb and Ta geochemical occurrences in S-type (Kagenfels) and I-S-type (Natzwiller) granites outlined in public domain data. Multi-element geochemical assays revealed the presence of fault-controlled Sn, W, Nb mineralisation assemblages along the margins of the Natzwiller and Kagenfels granites. Characteristic geochemical fractionation and principal component analysis (PCA) trends along with mineralogical evidence in the form of cassiterite, wolframite, ilmenorutile and columbite phases and muscovite&ndash, chlorite&ndash, tourmaline hydrothermal alteration association assemblages in stream sediments demonstrate that, in the northern Vosges, S-type and fractionated hybrid I-S-type granites are enriched in incompatible, late-stage magmatic elements. This is attributed to magmatic fractionation and hydrothermal alteration trends and the presence of fluxing elements in late-stage granitic melts. This study shows that the fractionated granite suites in the northern Vosges Mountains contain rare metal mineralisation indicators and therefore represent possible targets for follow-up mineral exploration. The application of automated mineralogy (QEMSCAN&reg, ) in regional stream sediment sampling added significant value by linking geochemistry and mineralogy.

The combination of complex, multiple minerogenic stages and mineral superposition during geological processes has resulted in dynamic spatial distributions and nonstationarity of geological variables. For example, geochemical elements exhibit clear spatial variability and trends with coverage type changes. Thus, bias is likely to occur under these conditions when general regression models are applied to mineral prospectivity mapping (MPM). In this study, we used a spatially weighted technique to improve general logistic regression and developed an improved model, i.e., the improved logistic regression model, based on a spatially weighted technique (ILRBSWT, version 1.0). The capabilities and advantages of ILRBSWT are as follows: (1) it is a geographically weighted regression (GWR) model, and thus it has all advantages of GWR when managing spatial trends and nonstationarity; (2) while the current software employed for GWR mainly applies linear regression, ILRBSWT is based on logistic regression, which is more suitable for MPM because mineralization is a binary event; (3) a missing data processing method borrowed from weights of evidence is included in ILRBSWT to extend its adaptability when managing multisource data; and (4) in addition to geographical distance, the differences in data quality or exploration level can be weighted in the new model.

The evaluation of economic potential of any hydrocarbon field involves the understanding of the reservoir lithofacies and porosity variations. This in turns contributes immensely towards subsequent reservoir management and field development. In this study, integrated 3D seismic data and well log data were employed to assess the quality and prospectivity of the delineated reservoirs (H1âH5) within the OPO field, western Niger Delta using a model-based seismic inversion technique. The model inversion results revealed four distinct sedimentary packages based on the subsurface acoustic impedance properties and shale contents. Low acoustic impedance model values were associated with the delineated hydrocarbon bearing units, denoting their high porosity and good quality. Application of model-based inverted velocity, density and acoustic impedance properties on the generated time slices of reservoirs also revealed a regional fault and prospects within the field. Keywords: Acoustic impedance, Reservoir characterization, Seismic inversion, Hydrocarbon exploration, Niger Delta

The article presents theoretical pre-requisites for gold mineralization in the Jurassic black shale strata of the Krasnaya Polyana geostructural zone of the North Caucasus. A brief historical review of investigation and extraction of gold in the area of the Mzymta and Shahe rivers was made. The search criteria and criteria of endogenous precious metal mineralization in black shale are identified: the presence of magmatic vein complexes in the region, lithostratigraphic and lithogeochemical barriers, deep-seated regional faults and other en echelon faults, sulphide mineralization. In 2013, during a geological field trip, the ore zone on the right side of the Mzymta River was located and investigated. Mineralized black shale and Mesozoic limestone cut through the intrusive body of gabbro-diorites, with a complex zonal structure. The microscopic analysis data showed that a significant part of the ore mineralization is represented by pyrite with globular structure, which is an important criterion in the genesis of sulfide deposits. Increased sulfide content, structural features of magmatic bodies, as well as chemical analysis data indicate their prospectivity for gold content.